The present invention generally relates to helical scan type magnetic recording apparatuses which form tracks mutually separated in a width direction of a magnetic tape, and more particularly to a helical scan type magnetic recording apparatus which records three kinds of signals constituting a color video signal on a plurality of oblique tracks which are mutually separated in the width direction of the magnetic tape by use of a plurality of pairs of rotary heads which simultaneously and independently form the plurality of oblique tracks, and also forms one or two audio tracks, a control track and a specific information signal recording track along a longitudinal direction of the magnetic tape by use of stationary heads.
A helical scan type magnetic recording and reproducing apparatus (hereinafter simply referred to as a VTR) which uses a magnetic tape having a width of 1/2 inch is presently used in various fields. However, in the VTR for home use, the frequency band in which the recording and reproduction can be performed is relatively narrow. For this reason, in the VTR for home use, a luminance signal separated from a color video signal is frequency-modulated and a carrier chrominance signal separated from the color video signal is frequency-converted into a low frequency range, and the frequency modulated luminance signal and the frequency converted carrier chrominance signal are frequency-division-multiplexed and recorded on and reproduced from the tape. In the present specification, such a recording and reproducing system in which the carrier chrominance signal is frequency-converted into the low frequency range will be referred to as a low-band conversion system. Further, in the VTR for home use, the tape utilization efficiency is improved by employing a system which does not form guard bands at the time of the recording and uses rotary heads having gaps of mutually different azimuth angles to record two mutually adjacent tracks.
On the other hand, in the VTR for business use such as broadcasting and especially in the case of a one-body type VTR having a camera unitarily built therein, there are demands to downsize the apparatus, reduce the weight of the apparatus and obtain a reproduced color video signal having a high picture quality. Hence, the luminance signal and color difference signals are recorded on independent tracks on the tape which has a width identical to that used in the VTR for home use by rotary heads so that a guard band is formed between two mutually adjacent tracks. In the present specification, such a recording and reproducing system will be referred to as a Y/C separation system.
According to the VTR employing the Y/C separation system, during a time period in which one rotary head records one field of the luminance signal on one track, another rotary head records one field of the color difference signals on another track. Thus, two tracks are simultaneously formed in each time period of one field. The tracks recorded with the luminance signal and the track recorded with the color difference signals are formed adjacent to each other along a longitudinal direction of the tape.
The luminance signal and the color difference signals are recorded on and reproduced from independent tracks on the tape according to the Y/C separation system. For this reason, although a moire occurs in the case of the VTR employing the low-band conversion system when the frequency modulated luminance signal and the frequency converted carrier chrominance signal are simultaneously recorded on the same track on the tape which is a non-linear transmission system, such a moire will not occur according to the VTR employing the Y/C separation system. In addition, it is possible to reserve sufficiently wide frequency bands for recording and reproducing the luminance signal and the color difference signals. Further, because the VTR employing the Y/C separation system does not record the frequency converted carrier chrominance signal by using the frequency modulated luminance signal as a bias signal, it is possible to improve the signal-to-noise (S/N) ratio of the reproduced color difference signals. As a result, it is possible to obtain a reproduced color video signal having a high picture quality compared to the VTR employing the low-band conversion system.
However, the tape utilization efficiency is poor according to the Y/C separation system because of the need to provide the guard band. Moreover, in the case where the rotary head crosses a guard band at the time of the reproduction and scans a track which is adjacent to the intended track which is to be scanned, the rotary head which should reproduce the luminance signal (or the color difference signals) will reproduce the color difference signals (or the luminance signal) since two mutually adjacent tracks are independently recorded with the luminance signal and the color difference signals. There is no field correlation between the reproduced signals from the two mutually adjacent tracks, and thus, it is impossible to eliminate the crosstalk by a crosstalk cancelling method which uses the field correlation as is done in the VTR for home use which employs the low-band conversion system. Hence, the VTR employing the Y/C separation system has a problem in that the crosstalk is conspicuous in the reproduced picture.
The conventional VTR employing the Y/C separation system simultaneously records and reproduces the luminance signal and the color difference signals on and from independent tracks on the tape by a pair of rotary heads having gaps of mutually different azimuth angles. For this reason, when a tracking error occurs at the time of the reproduction, there is a problem in that a time difference occurs between the reproduced luminance signal and the reproduced color difference signals from the pair of rotary heads.
Accordingly, in order to eliminate the problems described above, recording and reproducing apparatuses were previously proposed in a Japanese Utility Model Application No. 57-66496 (Japanese Laid-Open Utility Model Application No. 58-170012), Japanese Patent Application No. 60-35827 and Japanese Patent Application No. 60-35828 in which the applicant is the same as the assignee of the present application. According to the previously proposed apparatuses, three kinds of signals constituting the color video signal are recorded on and reproduced from a plurality of tracks which are formed in recording regions of the tape which are separated from each other in the width direction of the tape. Since the recording regions in which the plurality of tracks are simultaneously and independently formed on the tape are completely separated from each other, it is possible to prevent mutual interference among the signals reproduced from the tracks in the different recording regions and hence eliminate the problems of the conventional apparatus.
However, in the previously proposed apparatuses or the one-body type VTR for broadcasting use described before, three kinds of tracks are formed along the longitudinal direction of the tape by use of stationary heads in addition to the oblique tracks which are formed by the rotary heads. The three kinds of tracks are one or two audio tracks, a control track and a time code track.
The one or two audio tracks are recorded with audio signals, and the control track is recorded with a control pulse signal having a period of one frame, for example. The time code track is recorded with a time code signal which is used to detect an absolute address on the tape. The time code signal is in accordance with a standard set by Society of Motion Picture and Television Engineers (SMPTE), for example.
Out of the three kinds of tracks, the control track and the time code track are formed adjacent to each other at a lower end portion of the tape. Details of the track pattern used in the one-body type VTR for broadcasting use are disclosed in a Japanese journal "The Journal of the Institute of Television Engineers of Japan", April issue (1984), pages 96 and 97, for example. The reason why the control track and the time code track are formed at the lower end portion of the tape is as follows. Firstly, it is easier to record on a central portion of the tape the luminance signal and the color difference signals which are most important out of the information signals recorded on the tape. Secondly, a crosstalk introduced from an adjacent track when the control track and the time code track are formed adjacent to each other can be reduced by providing a guard band between the control track and the time code track.
However, the frequencies of the control pulse signal and the time code signal are relatively low, and the control pulse signal and the time code signal are usually recorded after the levels thereof are amplified due to the saturation recording which is employed. For this reason, since the stationary heads which form the control track and the time code track are arranged adjacent to each other, the control pulse signal and the time code signal which are to be recorded mutually interfere and this mutual interference may introduce undesirable effects on each other. Especially because the control pulse signal and the time code signal are timing signals related to time, the mutual interference should never occur.
On the other hand, due to the provision of the guard band between the control track and the time code track, a recordable region on the tape is not effectively utilized in the apparatuses described before.